Putting It To Work: New Publication Out of the Grouper Moon Project

Results from the study authored by J Egerton et al shows the visualization provided by the hydroacoustic technology used to evaluate size and location of the Nassau Grouper spawning aggregation off Little Cayman. Figure (c) Coral Reefs, 2017.
A team of REEF scientists and volunteers have visually monitored the Little Cayman spawning aggregation annually since 2002. Photo by Phil Bush.

A new publication in the scientific journal Coral Reefs was recently issued based on science conducted as part of REEF's Grouper Moon Project. The paper, titled "Hydroacoustics for the discovery and quantification of Nassau grouper (Epinephelus stratus) spawning aggregations", summarizes results from work conducted during the 2014 Grouper Moon Project field season in the Cayman Islands. Led by Jack Egerton from Bangor University in the UK, the research focused on the use of hydroacoustic technology as a means to monitor the status and ecology of fish spawning aggregations. Egerton was assisted by Grouper Moon scientists, Dr. Brice Semmens and Dr. Scott Heppell, as well as Grouper Moon collaborators from the Cayman Islands Department of Environment. Using a split-beam echo sounder, data were used to visualize and estimate fish abundance and biomass at three Nassau Grouper spawning aggregations in the Cayman Islands. The estimates were compared with diver-collected data. Additionally, the technology was used to examine fish aggregation locations in relation to protected zones.

Patterns in the acoustic abundance matched that observed by the visual estimates reported by our Grouper Moon diver teams - total numbers found at the Little Cayman aggregation were significanly higher than the depeleted aggregations found on Grand Cayman and Cayman Brac. 

Spawning aggregation location examined with reference to seasonal marine protected areas (Designated Grouper Spawning Areas) showed that the aggregations were partially outside these areas at Grand Cayman and very close to the boundary at Cayman Brac. The aggregation on Little Cayman appears to be contained within the protected zone (at least in 2014). However, we know from other Grouper Moon Project data that the fish spend a lot of time traveling in and out of the zone during the day. Additionally, in 2015, the aggregation on Little Cayman shifted a significant distance to the north of the historical location and partially out of the protected zone. The results of this study show the importance of making use of many different approaches for monitoring and aggregations in order to most effectively inform future management of aggregating fish species.

To read more about this study and others that have been published based on REEF's programs, visit www.REEF.org/db/publications. To learn more about the Grouper Moon Project, visit www.REEF.org/groupermoonproject.

Design by Joanne Kidd, development by Ben Weintraub